The subject matter disclosed herein relates to turbomachinery. More specifically, the subject disclosure relates to attachment of turbomachine blades and platforms to the turbomachine.
In a typical turbomachine (a gas turbine, steam turbine or the like), work is added to or extracted from a working fluid via one or more rows of blades or buckets, hereinafter referred to as blades. The rows of blades, which may be located in either or both of a compressor section and a turbine section of the turbomachine, are typically fixed to a wheel which is rotatable around a central axis of the turbomachine. The blades are located and secured to the wheel by inserting a base portion of individual blades which are configured with a dovetail shape into a corresponding dovetail slot in the wheel.
The blades of the typical turbomachine include an integral platform extending from the base of blade. When the blades are installed on the wheel, the platforms define an inner flowpath of the turbomachine. Design of the blade and platform are constrained by stresses on the airfoil shape during operation of the turbomachine, and materials for a blade casting are chosen to withstand those stresses. As a consequence, the platform area, which is subject to lower levels of stress, is often over-robust because of the material chosen, and as a result more costly and heavier than necessary. Further, the airfoil is subjected to different thermal boundary conditions than the platform and a thermal fight results from the one-piece airfoil and platform configuration thus increasing stresses on the component.